Wednesday, November 05, 2014

Aging - predictors of cognitive abilities.

The Oct. 31 issue of Science Magazine has a special section of articles on the aging brain. I point in particular to Underwood's article, "Starting young", which describes the followup on a Scottish national intelligence test performed on every 11 year old in the country in 1932 and 1947. The finding was that an individual's level of intelligence at age 11 is the most powerful predictor of late-life cognitive ability — not diet, social engagement, or any other virtuous activity. Scores at age 11 predicted about 50% of the variance in the IQs at age 77 in a cohort of individuals living in the Lothian region near Edinburgh (1641 of the original 5000 people tested were assessed.) Note the bottom line indicated in the final clip below:

By having an intelligence measure from even earlier in life, the Lothian studies are helping distinguish glitter from gold in the vast literature on factors correlated with cognition. A good recent example is Deary's analysis of the potential benefits of drinking, Thompson says. A smattering of correlational studies suggest that drinking small amounts of wine has positive effects on cognition late in life—indeed, Deary initially found a similar result when he first looked for a relationship between alcohol consumption and cognitive performance in the Lothian cohort. When he accounted for the participants' IQ scores on the Scottish Mental Survey, however, the perceived benefit dissolved. Rather than gaining cognitive benefit from drinking wine when they were older, “people who drank more were already likely to be smart,” Deary says.

The Lothian cohort has similarly challenged other reported influences on cognition, such as diet, body mass index, and caffeine consumption. None of those factors seems to have any effect on cognitive skills in the Lothian cohort when childhood intelligence is accounted for, Deary says. Even the effects of social and intellectual activity disappeared when he took into account how bright children were at age 11, possibly because those children are more likely to end up being socially and intellectually engaged.

And a final clip:

...the growing body of data from the Lothian Birth Cohort studies and other aging research supports a theory that some describe irreverently, and a little brutally, as the “water tank hypothesis”: The better put-together your brain is early on, thanks to good genes and, to some extent, a favorable early life environment, the more cognitive reserves you have to lose to neurodegeneration. In other words, Martin says, “the more you start out with in the tank, the longer it takes to draw down.”